title: [Observational studies in the era of evidence based medicine: short review on their relevance, taxonomy and designs].
abstract: In this review of the literature, we distinguish between experimental and observational studies, highlighting the importance that the later have gained in the era of evidence-based medicine. We further analyze the value of observational studies in light of experimental studies. We present a taxonomy for observational studies based on units of observation and measurement (cross-sectional or longitudinal). We distinguish between descriptive studies and analytical studies. Then, and given its specificity, we define and present a classification for ecological studies. We define and consider the advantages and disadvantages of cross-sectional, case control and cohort studies. We analyze the strength of the evidence given by each study design. We finished by examining what should guide the choice of a study design.
authors.affiliation: Unidade de Saúde Pública Internacional e Bioestatística, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisboa, Portugal. ifronteira@ihmt.unl.pt
authors.forename: Ines
authors.initials: I
authors.lastname: Fronteira
mesh_terms: D016022:Case-Control Studies; D015331:Cohort Studies; D019317:Evidence-Based Medicine; D064887:Observational Studies as Topic / Q000145:classification / Q000379:methods / Q000592:standards; D013223:Statistics as Topic